This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7 119 from the inventor""s application METHOD FOR MANUFACTURING A DRIVING PART OF AN INK JETTING APPARATUS filed with the Korean Industrial Property Office on Nov. 4, 1999 and there duly assigned Ser. No. 48546/1999.
1. Field of the Invention
The present invention relates to an ink jet apparatus, such as an inkjet printer or a facsimile machine. More particularly, the invention concerns an integrally formed driving module of an electrostatic attraction type inkjet apparatus, and a method for manufacturing the module.
2. Description of the Related Art
Generally, an ink jet apparatus is employed in a print head of an output device, such as an inkjet printer or and a facsimile machine. The apparatus forces a jet of ink from an ink chamber through a nozzle. Such fluid jet apparatus types include a thermal type, an electrostatic-attraction type, a piezoelectric type, and a thermo-compression type, the type depending on the method for applying physical force to the fluid.
An example of an electrostatic attraction type fluid jet apparatus is shown in FIG. 1. The fluid jet apparatus includes a driving module 20 and a nozzle module 40.
Driving module 20 includes a substrate 15, an oxide layer 14 laminated on substrate 15, a working fluid barrier 25 having a working fluid chamber 27, a lower electrode 17 disposed in working fluid chamber 27, a membrane 30 disposed on the upper portion of working fluid chamber 27, and an upper electrode 37 disposed on the upper portion of membrane 30. Working fluid chamber 27 is either kept in a vacuum state, or is filled with a working fluid having a high permittivity, to accelerate the generation of the electrostatic force which will be described below.
Nozzle module 40 includes an ink chamber barrier 45 having an ink chamber 57, and a nozzle plate 47 connected to the upper portion of ink chamber barrier 45. On the upper side of nozzle plate 47, a nozzle 49 is formed to permit the ink in ink chamber 57 to be forced therethrough. The ink is constantly supplied to ink chamber 57 from an ink supply (not shown in the drawings).
As the voltage is applied to upper and lower electrodes 37 and 17, a potential difference is generated between upper and lower electrodes 37 and 17. Membrane 30 is deformed toward the working fluid chamber 27. The force deforming the membrane 30 is obtained by the following formula:
F=eAV2/2D2
where e is the permittivity of the working fluid reserved in working fluid chamber 27, A is the area of upper electrode 37, V is the potential difference between upper and lower electrodes 37 and 17, and D is the distance between upper and lower electrodes 37 and 17.
Membrane 30 lowers pressure in ink chamber 57, causing the ink to be sucked into ink chamber 57 from the ink supply (not shown). When the application of the voltage ceases, membrane 30 recovers its initial state. Accordingly, pressure in ink chamber 57 then increases, so that the ink in ink chamber 57 is forced out through nozzle 49.
The driving module 20 of the above-described electrostatic attraction type ink jet apparatus is made by the following processes: FIGS. 2 to 9 show the manufacturing processes for driving module 20 of a conventional electrostatic attraction type ink jet apparatus. The method for manufacturing driving module 20 includes the steps of making membrane 30 and various other modules, separately, and then connecting separately made membrane 30 and the other modules.
Membrane 30 is made by the following processes: As shown in FIG. 2, membrane 30 of a polyamide material is applied on substrate 60 by a spin coater. An oxide layer 61 is then vapor-deposited on substrate 60. Then, as shown in FIG. 3, an O-ring 63 made of quartz glass is attached to membrane 30. Then, as shown in FIG. 4, substrate 30 and oxide layer 61 are separated from membrane 30.
Working fluid barrier 25 is made by the following processes: As shown in FIG. 5, a lower electrode 17 is formed on a substrate 15 by a photo etching process. Then, an oxide layer 14 is vapor-deposited on substrate 15. Then, as shown in FIG. 6, working fluid barrier 25 is made as the polyamide is applied on oxide layer 14 by the spin coater, and then the central portion thereof is etched by a photo etching process.
When working fluid barrier 25 is completed, as shown in FIG. 7, membrane 30 shown in FIG. 4 is attached to the upper portion of working fluid barrier 25. Membrane 30 is then turned over so that O-ring 63 is located at a lower position. Then, as shown in FIG. 8, O-ring 63 is removed, and an upper electrode 37 is vapor-deposited on membrane 30 as shown in FIG. 9. As a result, driving module 30 is completed. After that, nozzle module 40, which is obtained through a separate manufacturing process, is attached to driving module 30. That completes a conventional electrostatic attraction type ink jet apparatus.
The above-described conventional ink jet apparatus, however, has the following shortcoming. The membrane 30 is separately made from the other modules, and it takes several processes to complete membrane 30, such as attaching O-ring 63, and separating the substrate 60. Accordingly, additional processes are needed for attaching membrane 30 to working fluid barrier 25. Also, an additional wafer is needed to manufacture membrane 30.
In order to overcome the shortcoming of the conventional ink jet apparatus, another electrostatic attraction type inkjet apparatus has been suggested in which ink chamber barrier 45 of nozzle module 40 is integrally formed with membrane 30 during the manufacturing of nozzle module 40. Such an ink jet apparatus saves manufacturing processes since ink chamber barrier 45 and membrane 30 are integrally formed (i.e., as a unitary product) by one process. Such an inkjet apparatus employs a method of doping the area corresponding to the membrane to provide conductivity, however, because it is hard to make upper electrode 37 to generate an electrostatic attraction with lower electrode 17.
This suggested ink jet apparatus, however, has a further shortcoming in that it is difficult to maintain a fine gap between lower electrode 17 and membrane 30. According to the above-mentioned formula (F=eAV2/2D2), the electrostatic attraction is increased as the gap between lower and upper electrodes 17 and 37 is narrowed. In the above ink jet apparatus, however, the gap between lower and upper electrodes 17 and 37 is relatively large, so a higher potential difference is needed to generate an appropriate electrostatic attraction for deformation of membrane 30. Moreover, it is difficult to make thin membrane 30. Accordingly, higher force is required to deform the membrane 30, and thus the product requires a higher degree of electrostatic attraction.
It is an object of the present invention to provide an improved method for manufacturing a driving module for an electrostatic attraction type ink jet apparatus. The method of this invention makes membrane integral with a driving module. The membrane is not made separately. The resulting membrane is capable of generating electrostatic attraction efficiently, and performing a smooth jet operation.
The improved method for manufacturing a driving module of an ink jet apparatus includes the steps of: forming a working fluid chamber by etching a wafer; vapor-depositing a lower electrode in the working fluid chamber; attaching a polyamide sheet to the wafer; forming a membrane by etching the polyamide sheet; and vapor-depositing an upper electrode on the membrane. The working fluid chamber is formed by a wet etching process, and the membrane is formed by a dry etching process.